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piewie
21-08-2010, 09:53 PM
Hello Everyone

I have a high stage -10°C open Intercooler vessel (A) supplied with liquid from the receiver. The sub-cooled liquid is then supplied to the -32°C surge vessel from where it is pumped to the evaporators. There are 2 low stage compressors -40/-10 which discharge into the Intercooler (A). I am upgrading the control valve on the liquid supply to the Intercooler and need to check the kW to size the valve correctly.

My question is: Do I add the kW’s of the -32 system (evaporators fed from the -32 surge vessel) and the kW’s of the 2 -40/-10 compressors? Or is it a little more complicated than that?

Any help greatly appreciated.
RANGER1
21-08-2010, 10:14 PM
piewie ,
I think you only need total of -10 compressors in KW as all flash gas from liquid line goes through these machines , as well as load from intercooler .
Allow for minimun pressure drop you may get across valve so it can handle all conditions comfortably ie low head pressures in winter etc .
A modulating valve would be the best option to smooth out loads on -10 compressors .
piewie
21-08-2010, 10:38 PM
Thanks Ranger1 but I do not think that will answer the question as our -10 compressors are connected via a common suction to our other -10 surge vessel so the work being done by the -10 compressors comes from two separate sources. What about my original idea?;)
RANGER1
21-08-2010, 11:03 PM
Where does the -40 system get its subcooled or liquid make up liquid from ?
piewie
21-08-2010, 11:18 PM
The -40 has a seperate surge which gets it’s liquid from the other -10 surge.
RANGER1
21-08-2010, 11:53 PM
You have to determine loads from each -10 systems .
Low side load has nothing to do with sizing of high side makeup valve .
Work out maximum load compressor wise for each -10 & that will be your answer simply put .
Segei
22-08-2010, 03:24 AM
Make up liquid from HPR goes to intermediate pressure receiver(IPR). Portion of this liquid will flash. Second portion will subcool -32C liquid. Third portion will desuperheat hot gas of -40C compressors. Desuperheating and subcooling loads depend of total load(-32 or -40). For example. -32 load is 100 KW. 10% of this load or 10 KW is subcooling. The same approach is for desuperheating.